Big trees boost city life

A gang gang pokes its head out from its nest in a gum tree. Photo by Pierre Pouliquin flickr.com

New research from The Australian National University has revealed for the first time the role large trees play in sustaining biodiversity and bird life in urban environments.

The study, led by Karen Stagoll, a PhD candidate in the ANU Fenner School of Environment and Society, examined large eucalypt trees in small suburban parks across Canberra. The team’s study is the first of its kind in the world and clearly shows that large trees in urban environments provide habitat resources crucial for wildlife.

"Large trees are considered ’keystone structures’, or ones which provide resources like food, nest sites and shelter for wildlife, in agricultural and forestry production landscapes," said Ms Stagoll. "But research demonstrating this in urban landscapes was urgently needed.

"We found that parks with more large eucalypts had more bird species and higher bird numbers, including more native woodland-dependent birds, some of which are declining in Canberra and the surrounding region. Birds were also more likely to breed in parks with large trees.

"We also found that if parks had really large, old trees they had more birds than parks with only smaller trees."

Ms Stagoll said that it is vital that large trees in urban environments are managed properly if cities are to maintain a diversity of wildlife.

"Losing large trees from cities may have far-reaching ecological consequences that may undermine other wildlife conservation measures," she said.

"Large eucalypts are protected in the ACT, but measures may not go far enough. We found that 14 per cent of trees measured were significantly important for birds but miss out on formal protection. It is likely that similar trees are at risk in other cities in Australia and the rest of the world.

"Public safety dangers posed by large, old trees should be managed by strategies other than tree removal, for example fencing off risky areas or using landscaping to minimise risk. We also need to plan for the future if we want to keep large trees and our native bird species within the city limits. It takes decades for a newly planted sapling to grow into a large tree, so we need to think and act early."